Display device

ABSTRACT

Display of a display device is made less likely to appear divided when a plurality of display panels are used as one screen. Provided is a display device including two display units and a foldable housing that includes a joint portion between the two display units and supports the two display units. Each display unit includes a display panel including a display region and a non-display region and a support having a first surface overlapped with the display region and a second surface that meets the first surface and is overlapped with the non-display region. The two display units are placed in the housing in an opened state such that the first surfaces of the supports face the same direction and the second surfaces of the supports face each other.

TECHNICAL FIELD

The present invention relates to a display device, an electronic device,or a manufacturing method thereof. The present invention particularlyrelates to a display device or an electronic device utilizingelectroluminescence (hereinafter also referred to as EL) or amanufacturing method thereof.

BACKGROUND ART

Recent display devices are expected to be applied to a variety of usesand become diversified. For example, display devices for mobile devicesand the like are required to be small, thin, and lightweight. Inaddition, display devices desirably have large screens (wide displayregions), and a reduction in the area of a display device except adisplay region (what is called a narrower bezel) is required.

Light-emitting elements utilizing EL (also referred to as EL elements)have features such as ease of thinning and lightening, high-speedresponse to input signal, and driving with a direct-current low voltagesource; therefore, application of the light-emitting elements to displaydevices has been proposed.

For example, Patent Document 1 discloses a foldable portablecommunication device that has reduced size and weight and that includesa plurality of displays and can be opened and closed so as to have alarge screen.

Patent Document

-   [Patent Document 1] Japanese Published Patent Application No.    2000-184026

DISCLOSURE OF INVENTION

However, since each display has a non-display region that surrounds adisplay region, in the structure of Patent Document 1, the non-displayregion exists at the joint between the two displays and in the vicinitythereof. The wider the non-display region is, the more divided an imagedisplayed with the plurality of displays appears to a viewer.

An object of one embodiment of the present invention is to provide anovel display device or electronic device. Another object of oneembodiment of the present invention is to provide a display device or anelectronic device of which display is less likely to appear divided whena plurality of display panels are used as one screen. Another object ofone embodiment of the present invention is to provide a small displaydevice or electronic device. Another object of one embodiment of thepresent invention is to provide a lightweight display device orelectronic device. Another object of one embodiment of the presentinvention is to provide a display device or an electronic device with anarrow bezel. Another object of one embodiment of the present inventionis to provide a display device or an electronic device that is lesslikely to be broken.

In one embodiment of the present invention, there is no need to achieveall the above objects.

One embodiment of the present invention is a display device includingtwo display units and a foldable housing that includes a joint portionbetween the two display units and supports the two display units. Eachdisplay unit includes a display panel including a display region and anon-display region and a support having a first surface overlapped withthe display region and a second surface that meets the first surface andis overlapped with the non-display region. The two display units areplaced in the housing in an opened state such that the first surfaces ofthe supports face the same direction and the second surfaces of thesupports face each other.

In the above structure, the display panel preferably has flexibility.

In the above structure, the display region preferably overlaps with thesecond surface.

In the above structure, the two display units are preferably placed inthe housing in an opened state to be in contact with each other suchthat the second surfaces of the supports face each other.

In the above structure, the two display units are preferably placed soas to be detachable from the housing.

In the above structure, the distance between the two display units ispreferably adjustable. For example, it is preferable that at least onedisplay unit can be moved toward the other display unit.

In the above structure, the support preferably has a third surface thatis opposite to the second surface and is overlapped with the non-displayregion of the display panel. Further, the third surface is preferablyoverlapped with the display region.

Embodiments of the present invention also include an electronic deviceincluding the above display device.

In one embodiment of the present invention, a novel display device orelectronic device can be provided. In one embodiment of the presentinvention, a display device or an electronic device of which display isless likely to appear divided when a plurality of display panels areused as one screen can be provided. In one embodiment of the presentinvention, a small display device or electronic device can be provided.In one embodiment of the present invention, a lightweight display deviceor electronic device can be provided. In one embodiment of the presentinvention, a display device or an electronic device with a narrow bezelcan be provided. In one embodiment of the present invention, a displaydevice or an electronic device that is less likely to be broken can beprovided.

BRIEF DESCRIPTION OF DRAWINGS

FIGS. 1A to 1D illustrate examples of a display device and a displayunit.

FIGS. 2A to 2D illustrate an example of a display device.

FIGS. 3A to 3C illustrate examples of a display device and a displayunit.

FIGS. 4A and 4B illustrate an example of a display device.

FIGS. 5A to 5C illustrate an example of a display device.

FIGS. 6A and 6B each illustrate an example of a housing.

FIGS. 7A and 7B each illustrate an example of a display panel.

FIGS. 8A and 8B illustrate an example of a display panel of oneembodiment of the present invention.

FIGS. 9A and 9B each illustrate an example of a display panel of oneembodiment of the present invention.

FIGS. 10A and 10B each illustrate an example of a display panel of oneembodiment of the present invention.

FIGS. 11A and 11B each illustrate an example of a display panel of oneembodiment of the present invention.

FIGS. 12A to 12C illustrate an example of a method for manufacturing adisplay panel of one embodiment of the present invention.

FIGS. 13A to 13C illustrate an example of a method for manufacturing adisplay panel of one embodiment of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiments will be described in detail with reference to drawings. Notethat the present invention is not limited to the description below, andit is easily understood by those skilled in the art that various changesand modifications can be made without departing from the spirit andscope of the present invention. Therefore, the present invention shouldnot be construed as being limited to the description in the followingembodiments.

Note that in the structures of the invention described below, the sameportions or portions having similar functions are denoted by the samereference numerals in different drawings, and description of suchportions is not repeated. Further, the same hatching pattern is appliedto portions having similar functions, and the portions are notespecially denoted by reference numerals in some cases.

In addition, the position, size, range, or the like of each structureillustrated in drawings and the like is not accurately represented insome cases for easy understanding. Therefore, the disclosed invention isnot necessarily limited to the position, the size, the range, or thelike disclosed in the drawings and the like.

Embodiment 1

Display devices of embodiments of the present invention will bedescribed with reference to FIGS. 1A to 1D, FIGS. 2A to 2D, FIGS. 3A to3C, FIGS. 4A and 4B, FIGS. 5A to 5C, FIGS. 6A and 6B, and FIGS. 7A and7B.

<Structure of Display Device of One Embodiment of the Present Invention>

A display device of one embodiment of the present invention includes twodisplay units and one housing. Each display unit includes a displaypanel including a display region and a non-display region and a supporthaving a first surface that is overlapped with the display region and asecond surface that meets the first surface and is overlapped with thenon-display region. The housing is foldable. The housing includes ajoint portion between the two display units. The housing supports thetwo display units. The two display units are placed in the housing in anopened state with the first surfaces of the supports facing the samedirection and the second surfaces of the supports facing each other.Display in the display regions of the display panels, which overlap withthe first surfaces of the supports, is viewed by a user of the displaydevice. Note that in one embodiment of the present invention, a firstsurface of a support refers to a surface that is overlapped with adisplay region of a display panel without any other surface of thesupport positioned therebetween. Similarly, in one embodiment of thepresent invention, a second surface of a support refers to a surfacethat is overlapped with a non-display region of a display panel withoutany other surface of the support positioned therebetween.

The display device of one embodiment of the present invention isfoldable. Accordingly, the user can fold the display device into a smallshape and carry it easily. Further, the user can view large-screendisplay by opening the display device and using the two display units asone screen. In the display device of one embodiment of the presentinvention, almost no non-display region exists (or a non-display regiondoes not exist) between the display region in one display unit and thedisplay region in the other display unit; thus, display is less likelyto appear divided when the two display units are used as one screen.Moreover, even when the display device is opened and closed repeatedly,the display panel itself is not deformed (not bent orexpanded/contracted). In other words, for example, a decrease in thelifetime of the display panel due to deformation is reduced and thedisplay device of one embodiment of the present invention has highreliability.

First, an example of a structure of a display device is described.

FIG. 1A is a perspective view of a display device 110 that is beingopened, and FIG. 1B is a perspective view of the display device 110 thatis folded.

The display device 110 includes a housing 103 and two display units 101.The two display units 101 may have the same structure or differentstructures.

The housing 103 is foldable. The housing 103 includes a joint portion106 (e.g., a hinge) positioned between the two display units 101(specifically, the joint portion 106 overlaps with part of the twodisplay units 101 between the two display units 101). The housing 103supports the two display units 101.

FIG. 1A shows an example in which the housing 103 has a depressedportion and the display units 101 are placed in the depressed portion.The display units 101 may be bonded to the housing 103 or may bedetachably mounted thereon.

The display device 110 is foldable. Accordingly, a user can fold thedisplay device 110 into a small shape and carry it easily. Further, theuser can view large-screen display by opening the display device 110 andusing the two display units as one screen. Moreover, even when thedisplay device 110 is opened and closed repeatedly, the display unit 101itself is not deformed. In other words, for example, a decrease in thelifetime of the display unit 101 due to deformation is reduced and thedisplay device 110 has high reliability.

FIGS. 1C and 1D each illustrate an example of a structure of the displayunit 101.

FIG. 1C shows a perspective view of a display unit 101 a and plan viewsseen in the directions of arrow A and arrow B in the perspective view.FIG. 1D shows a perspective view of a display unit 101 b and plan viewsseen in the directions of arrow A and arrow B in the perspective view.

The display units 101 a and 101 b each include a support 201 and adisplay panel 203. The display panel 203 has a display region 203 a anda non-display region 203 b.

In the display units 101 a and 101 b, the display region 203 a overlapswith a first surface of the support 201 that can be viewed in thedirection of arrow A in the perspective view, and the non-display region203 b overlaps with a second surface of the support 201 that can beviewed in the direction of arrow C in the perspective view. Further, inthe display unit 101 b, the non-display region 203 b overlaps with athird surface of the support 201 that is opposite to the second surface.Here, in the plan views in FIGS. 1C and 1D that are seen in thedirection of arrow B in the perspective views, the non-display region203 b in the display panel 203 is indicated by dotted circles.

In the display panel, for example, the non-display region is provided tosurround the display region. In one embodiment of the present invention,as in the display unit 101 a, one of two surfaces in series of thesupport 201 (first surface) is overlapped with the display region 203 a,and the other (second surface) is overlapped with the non-display region203 b. When the display panel 203 overlaps with two or more surfaces ofthe support 201, the proportion of the area of the first surfaceoccupied by the display region 203 a is increased and the display unitcan have a narrow bezel, as compared with the case where the displaypanel 203 overlaps with only one surface of the support 201.

Further, when the display panel 203 overlaps with three or more surfacesof the support 201 and the non-display region 203 b overlaps with thetwo separate surfaces among three surfaces in series of the support 201(second and third surfaces) and the display region 203 a overlaps withthe surface between the two separate surfaces (first surface), as in thedisplay unit 101 b, the proportion of the area of the first surfaceoccupied by the display region 203 a is further increased and thedisplay unit can have a narrower bezel.

When at least one of the display units 101 a and 101 b is used for thedisplay units 101 in FIG. 1A, in the vicinity of a region where the twodisplay units 101 are in contact with each other, almost no non-displayregion exists between the display region 203 a in one display unit andthe display region 203 a in the other display unit. Therefore, displayof the display device is less likely to appear divided when the twodisplay units 101 are used as one screen.

As shown in FIGS. 1C and 1D, the non-display region 203 b may overlapwith the surface opposite to the first surface.

The non-display region 203 b can overlap with the surface of the support201 opposite to the first surface and the surface meeting the firstsurface (the second surface or the third surface); accordingly, a bezelof a display panel included in a display unit of one embodiment of thepresent invention does not need to be narrow. For example, in the caseof a display panel using an organic EL element, the wider the area ofthe non-display region 203 b surrounding the display region 203 a is,the longer the distance between the edge of the display panel and theorganic EL element is. This is preferable because an impurity such asmoisture or oxygen is less likely to enter (or reach) the organic ELelement from the outside of the display panel, leading to higherreliability of the display panel.

In the display panels shown in FIGS. 7A and 7B, a region 301 is a regionof the display panel that overlaps with the first surface of the support201, and a region 303 is a region of the display panel that overlapswith the surface of the support 201 opposite to the first surface or thesurface meeting the first surface (the second surface or the thirdsurface). In FIGS. 7A and 7B, the area of the display region 203 a isthe same. The display region 203 a is entirely included in a regionoverlapping with the first surface. In FIG. 7B, the region 303 is widerthan in FIG. 7A. This is preferable because an external impurity such asmoisture or oxygen is less likely to reach the organic EL elementthrough the edge of the display panel. For example, the area of a regionwhere the display panel 203 overlaps with the surface of the support 201opposite to the first surface is preferably 10% or more, furtherpreferably 30% or more, still further preferably 50% or more of the areaof the surface opposite to the first surface.

Further, as shown in FIGS. 1C and 1D, the display region 203 apreferably overlaps with the second surface as well as the firstsurface. When at least one of the display units 101 a and 101 b is usedfor the display units 101 in FIG. 1A, in the vicinity of a region wherethe two display units 101 are in contact with each other, almost nonon-display region exists between the display region 203 a in onedisplay unit and the display region 203 a in the other display unit.Therefore, display of the display device is less likely to appeardivided when the two display units 101 are used as one screen.

Moreover, in the display unit 101 b, the display region 203 a preferablyoverlaps with the third surface, in which case the proportion of thearea of the first surface occupied by the display region 203 a isincreased.

Next, another example of a structure of a display device is described.

FIG. 2A is a plan view of a display device 120 that is opened. FIG. 2Bis a plan view of the display device 120 that is folded. FIG. 2C is aperspective view of the display device 120 that is opened. FIG. 2D is aperspective view of the display device 120 that is folded.

The display device 120 includes a housing 103 a and two display units(each display unit includes the support 201 and the display panel 203).The distance between the two display units is adjustable. In a displaydevice of one embodiment of the present invention, at least one of twodisplay units can be moved in the lateral direction of FIG. 2A. Thedisplay device 120 is shown as an example in which both of the twodisplay units can be moved in the lateral direction of FIG. 2A.

Here, in the display device 120, each of the two display units is adisplay unit 101 c shown in FIG. 3A; however, one embodiment of thepresent invention is not limited thereto. For example, any of thedisplay units 101 a and 101 b shown in FIGS. 1C and 1D and a displayunit 101 d shown in FIG. 3B can be used. For example, one of the twodisplay units may be the display unit 101 a and the other may be thedisplay unit 101 c. Note that the structure of the display unit 101 c isthe same as that of the display unit 101 a except for having aprojection 205, and the structure of the display unit 101 d is the sameas that of the display unit 101 b except for having the projection 205.

FIG. 6A shows a perspective view and a plan view of the housing 103 a.The housing 103 a is foldable. The housing 103 a includes the jointportion 106 positioned between the two display units. The housing 103 ahas a depressed portion and supports two display units placed in thedepressed portion. FIGS. 2A to 2D show an example in which display unitsare detachably placed in the depressed portion of the housing 103 a.

In FIG. 2A, the two display units can be moved in the lateral directionof the drawing and can be fixed to the housing 103 a with the projection205 (e.g., a nail, a hook, a lug, a tab, or a claw) of the support 201and a projection 207 (e.g., a nail, a hook, a lug, a tab, or a claw) ofthe housing 103 a. There is no particular limitation on the positions ofthe projection 205 and the projection 207. For example, the projection207 is provided in contact with the bottom surface or a side surface ofthe depressed portion of the housing 103 a.

FIGS. 2A to 2D show a state where the two display units are apart fromeach other. It is possible to bring the two display units in contactwith or close to each other by moving at least one of the display units.Such a state will be described in detail using a display device 140shown later in drawings.

When a display device that is opened performs display, the two displayunits are preferably in contact with each other. Specifically, the twodisplay units are preferably placed in the housing 103 a in an openedstate to be in contact with each other such that the second surfaces ofthe supports 201 face each other. In that case, display is less likelyto appear divided when the two display units are used as one screen.Note that in the case where the two display units of the opened displaydevice independently perform display, the positions of the two displayunits are not particularly limited.

Further, when the display device is folded, the two display units arepreferably apart from each other. In that case, the edges of the displayunits do not exist on the same plane as the edge of the folded housing103 a at the side surface including the joint portion 106 of the displaydevice, which is shown in FIG. 2D; thus, the supports 201 and thedisplay panels 203 can be prevented from being damaged and broken.

In FIG. 2B, the display device is folded such that the display units areplaced on the inner side of the display device; however, one embodimentof the present invention is not limited thereto.

A display device 130 shown in FIG. 3C is folded such that the displayunits are placed on the outer side of the display device. Accordingly,even in the folded state, the display units on two opposite surfaces ofthe display device 130 can independently perform display.

A display device of one embodiment of the present invention can befolded such that the display units are on either the outer side or theinner side of the display device. With such a structure, it is possiblenot only to open the display device and view the display on the displayunits but also to fold the display device such that the display unitsare on the outer side of the display device and view the display on thedisplay units. Further, folding the display device such that the displayunits are on the inner side of the display device enables the displaypanels to be prevented from being damaged and broken when the displaydevice is not in use.

Another example of a structure of a display device will be described.

FIG. 4A and FIG. 5A are plan views of the display device 140 that isopened. FIG. 4B and FIG. 5B are perspective views of the display device140 that is opened. FIG. 5C is a perspective view of the display device140 that is folded. FIGS. 4A and 4B show the case where two displayunits are not in contact with each other, and FIGS. 5A to 5C show thecase where two display units are in contact with each other.

The display device 140 includes a housing 103 b and two display units(each display unit includes the support 201 and the display panel 203).Here, each of the two display units is the display unit 101 c shown inFIG. 3A.

FIG. 6B shows a perspective view and a plan view of the housing 103 b.The housing 103 b is foldable. The housing 103 b includes the jointportion 106 positioned between the two display units. The housing 103 bhas a groove portion (depressed portion) and supports two display unitsplaced in the groove portion. FIGS. 4A and 4B and FIGS. 5A to 5C showexamples in which the display units are detachably placed in the grooveportion of the housing 103 b. The housing 103 b covers part of the firstsurface of each support 201 (preferably, a portion overlapped with thenon-display region of the display panel 203). Thus, the display deviceis less likely to be broken down into the display units and the housing.

In FIG. 4A and FIG. 5A, the two display units can be moved in thelateral direction of the drawing and can be fixed to the housing 103 bwith the projection 205 (e.g., a nail, a hook, a lug, a tab, or a claw)of the support 201 and the projection 207 (e.g., a nail, a hook, a lug,a tab, or a claw) of the housing 103 b.

It is possible to bring the two display units of the display device 140in contact with or close to each other by moving at least one of the twodisplay units.

When a display device that is opened performs display, the two displayunits are preferably in contact with each other, as shown in FIGS. 5Aand 5B. Specifically, the two display units are preferably placed in thehousing 103 b in an opened state to be in contact with each other suchthat the second surfaces of the supports 201 face each other. In thatcase, display is less likely to appear divided when the two displayunits are used as one screen.

Further, when the display device is folded, the two display units arepreferably apart from each other (refer to the perspective view of thedisplay device 120 in FIG. 2D). When the two display units are incontact with each other, as shown in FIG. 5C, the edges of the displayunits exist on the same plane as the edge of the folded housing 103 b atthe side surface including the joint portion 106 of the display device;thus, the supports 201 and the display panels 203 are damaged and brokenin some cases.

<Materials that can be Used for the Display Device of One Embodiment ofthe Present Invention>

Next, examples of materials that can be used for the display device ofone embodiment of the present invention are described.

[Housing and Support]

The housing and the support can be formed using plastic, a metal, analloy, rubber, or the like. Plastic, rubber, or the like is preferablyused because it can form a housing or a support that is lightweight andless likely to be broken.

When the display unit is bonded to the housing or when the display panelis bonded to the support, any of a variety of adhesives can be used, andfor example, a resin that is curable at room temperature (e.g., atwo-component-mixture-type resin), a light curable resin, athermosetting resin, or the like can be used. Alternatively, asheet-like adhesive may be used.

[Display Panel]

The display panel preferably has flexibility. Note that the displaypanel does not necessarily have flexibility. For example, a displaypanel that is shaped in advance to fit the shape of the display devicemay be used.

There is no particular limitation on the display element included in thedisplay panel, for which a liquid crystal element, a light-emittingelement (such as a light-emitting diode, an organic EL element, or aninorganic EL element), a plasma tube, or the like can be used.

For example, it is preferable to use an organic EL element because itmakes it easy to provide a lightweight flexible display panel.

The display panel may be an active matrix type or a passive matrix type.

In the case where the display panel is an active matrix type, thestructure of a transistor included in the display panel is not limited,and either a top-gate transistor or a bottom-gate transistor may beused. In addition, either an n-channel transistor or a p-channeltransistor may be used. Furthermore, there is no particular limitationon a material used for the transistor. For example, a transistor inwhich silicon or an oxide semiconductor such as an In—Ga—Zn-based metaloxide is used in a channel formation region can be employed.

The display panel may include a sensor such as a touch sensor.

A substrate included in the display panel is preferably formed using amaterial with high toughness. In that case, a display panel with highimpact resistance that is less likely to be broken can be provided. Forexample, when an organic resin substrate or a substrate formed using athin metal material or a thin alloy material is used, the display panelcan be lightweight and less likely to be broken as compared with thecase where a glass substrate is used.

A flexible display panel can be manufactured using a variety ofmanufacturing methods. It is possible to form elements (e.g., a displayelement, a transistor, and a color filter) directly over a flexiblesubstrate in the case where the flexible substrate can withstand thetemperatures in the manufacturing process.

When a material which is flexible but has high water permeability andlow heat resistance (e.g., resin) needs to be used for a substrate, thesubstrate cannot be exposed to high temperature in the manufacturingprocess; thus, conditions for forming the elements over the substrateare limited. In such a case, a flexible display panel can bemanufactured by a technique in which some components of a display panelare formed over a formation substrate having high heat resistance, andthen the components are transferred from the formation substrate to aflexible substrate. Since a transistor and the like can be formed over aformation substrate having high heat resistance, a highly reliabletransistor and an insulating layer with sufficiently low waterpermeability can be formed. Further, these components are transferred toa flexible substrate. In this manner, a flexible display panel with highreliability can be manufactured.

This embodiment can be combined with any other embodiment asappropriate.

Embodiment 2

In this embodiment, a flexible display panel that can be used for thedisplay device of one embodiment of the present invention is describedwith reference to FIGS. 8A and 8B, FIGS. 9A and 9B, FIGS. 10A and 10B,FIGS. 11A and 11B, FIGS. 12A to 12C, and FIGS. 13A to 13C. When thedisplay panel described in this embodiment is bent, the minimumcurvature radius of a bent portion of the display panel can be greaterthan or equal to 1 mm and less than or equal to 150 mm, greater than orequal to 1 mm and less than or equal to 100 mm, greater than or equal to1 mm and less than or equal to 50 mm, greater than or equal to 1 mm andless than or equal to 10 mm, or greater than or equal to 2 mm and lessthan or equal to 5 mm. The display panel in this embodiment is free frombreakage of an element even when bent with a small curvature radius(e.g., greater than or equal to 2 mm and less than or equal to 5 mm) andhas high reliability. Bending the display panel with a small curvatureradius can make the display device of one embodiment of the presentinvention thin. Bending a light extraction portion 224 with a largecurvature radius (e.g., greater than or equal to 5 mm and less than orequal to 100 mm) can provide a large display portion on a side surfaceof the display device. There is no limitation on the direction in whichthe display panel in this embodiment is bent. Further, the number ofbent portions may be one or more than one.

Specific Example 1

FIG. 8A is a plan view of a display panel, and FIG. 8B is an example ofa cross-sectional view taken along dashed-dotted line A1-A2 in FIG. 8A.

The display panel in FIG. 8B includes a substrate 221, a bonding layer223, an insulating layer 225, a plurality of transistors, a conductivelayer 157, an insulating layer 227, an insulating layer 229, a pluralityof light-emitting elements, an insulating layer 211, a sealing layer213, an insulating layer 261, a coloring layer 259, a light-blockinglayer 257, an insulating layer 255, a bonding layer 258, and a substrate222.

The conductive layer 157 is electrically connected to an FPC 228 via aconnector 215.

A light-emitting element 230 includes a lower electrode 231, an EL layer233, and an upper electrode 235. The lower electrode 231 is electricallyconnected to a source electrode or a drain electrode of a transistor240. An end portion of the lower electrode 231 is covered with theinsulating layer 211. The light-emitting element 230 has a top emissionstructure. The upper electrode 235 has a light-transmitting property andtransmits light emitted from the EL layer 233.

The coloring layer 259 is provided to overlap with the light-emittingelement 230, and the light-blocking layer 257 is provided to overlapwith the insulating layer 211. The coloring layer 259 and thelight-blocking layer 257 are covered with the insulating layer 261. Thespace between the light-emitting element 230 and the insulating layer261 is filled with the sealing layer 213.

The display panel includes a plurality of transistors in the lightextraction portion 224 and a driver circuit portion 226. The transistor240 is provided over the insulating layer 225. The insulating layer 225and the substrate 221 are attached to each other with the bonding layer223. The insulating layer 255 and the substrate 222 are attached to eachother with the bonding layer 258. It is preferable to use films with lowwater permeability for the insulating layer 225 and the insulating layer255, in which case an impurity such as water can be prevented fromentering the light-emitting element 230 or the transistor 240, leadingto improved reliability of the display panel.

As an insulating film with low water permeability, a film containingnitrogen and silicon (e.g., a silicon nitride film or a silicon nitrideoxide film), a film containing nitrogen and aluminum (e.g., an aluminumnitride film), or the like can be used. Alternatively, a silicon oxidefilm, a silicon oxynitride film, an aluminum oxide film, or the like canbe used.

For example, the water vapor transmittance of the insulating film withlow water permeability is lower than or equal to 1×10⁻⁵ [g/m²·day],preferably lower than or equal to 1×10⁻⁶ [g/m²·day], further preferablylower than or equal to 1×10⁻⁷ [g/m²·day], still further preferably lowerthan or equal to 1×10⁻⁸ [g/m²·day].

The display panel in Specific Example 1 can be manufactured in thefollowing manner: the insulating layer 225, the transistor 240, and thelight-emitting element 230 are formed over a formation substrate withhigh heat resistance; the formation substrate is separated; and theinsulating layer 225, the transistor 240, and the light-emitting element230 are transferred to the substrate 221 and attached thereto with thebonding layer 223. The display panel in Specific Example 1 can bemanufactured in the following manner: the insulating layer 255, thecoloring layer 259, and the light-blocking layer 257 are formed over aformation substrate with high heat resistance; the formation substrateis separated; and the insulating layer 255, the coloring layer 259, andthe light-blocking layer 257 are transferred to the substrate 222 andattached thereto with the bonding layer 258.

In the case where a material with low heat resistance (e.g., resin) isused for a substrate, it is impossible to expose the substrate to hightemperature in the manufacturing process. Thus, there is a limitation onconditions for forming a transistor and an insulating film over thesubstrate. Further, in the case where a material with high waterpermeability (e.g., resin) is used for a substrate of a display panel,it is preferable to expose the substrate to high temperature and form afilm with low water permeability between the substrate and alight-emitting element. In the manufacturing method of this embodiment,a transistor and the like can be formed over a formation substratehaving high heat resistance; thus, the substrate can be exposed to hightemperature and a highly reliable transistor and an insulating film withsufficiently low water permeability can be formed. Then, the transistorand the insulating film are transferred to a substrate with low heatresistance, whereby a highly reliable display panel can be manufactured.Thus, with one embodiment of the present invention, a thin or/andlightweight display panel with high reliability can be provided. Detailsof the manufacturing method will be described later.

The substrate 221 and the substrate 222 are each preferably formed usinga material with high toughness. Thus, a display panel with high impactresistance that is less likely to be broken can be provided. Forexample, when the substrate 222 is an organic resin substrate and thesubstrate 221 is a substrate formed using a thin metal material or athin alloy material, the display panel can be lightweight and lesslikely to be broken as compared with the case where a glass substrate isused.

A metal material and an alloy material, which have high thermalconductivity, are preferred because they can easily conduct heat to thewhole substrate and accordingly can prevent a local temperature rise inthe display panel. The thickness of a substrate using a metal materialor an alloy material is preferably greater than or equal to 10 μm andless than or equal to 200 μm, further preferably greater than or equalto 20 μm and less than or equal to 50 μm.

Further, when a material with high thermal emissivity is used for thesubstrate 221, the surface temperature of the display panel can beprevented from rising, leading to prevention of breakage or a decreasein reliability of the display panel. For example, the substrate 221 mayhave a stacked structure of a metal substrate and a layer with highthermal emissivity (the layer can be formed using a metal oxide or aceramic material, for example).

Specific Example 2

FIG. 9A shows another example of the light extraction portion 224 in thedisplay panel of one embodiment of the present invention. The displaypanel shown in FIG. 9A is capable of touch operation. In the followingspecific examples, description of components similar to those inSpecific Example 1 is omitted.

The display panel in FIG. 9A includes the substrate 221, the bondinglayer 223, the insulating layer 225, a plurality of transistors, theinsulating layer 227, the insulating layer 229, a plurality oflight-emitting elements, the insulating layer 211, an insulating layer217, the sealing layer 213, the insulating layer 261, the coloring layer259, the light-blocking layer 257, a plurality of light-receivingelements, a conductive layer 281, a conductive layer 283, an insulatinglayer 291, an insulating layer 293, an insulating layer 295, theinsulating layer 255, the bonding layer 258, and the substrate 222.

Specific Example 2 includes the insulating layer 217 over the insulatinglayer 211. The space between the substrate 222 and the substrate 221 canbe adjusted with the insulating layer 217.

FIG. 9A shows an example in which a light-receiving element is providedbetween the insulating layer 255 and the sealing layer 213. Since thelight-receiving element can be placed to overlap with anon-light-emitting region (e.g., a region where the light-emittingelement is not provided, such as a region where a transistor or a wiringis provided) of the display panel, the display panel can be providedwith a touch sensor without a decrease in the aperture ratio of a pixel(light-emitting element).

As the light-receiving element included in the display panel of oneembodiment of the present invention, for example, a PN photodiode or aPIN photodiode can be used. In this embodiment, a PIN photodiodeincluding a p-type semiconductor layer 271, an i-type semiconductorlayer 273, and an n-type semiconductor layer 275 is used as thelight-receiving element.

Note that the i-type semiconductor layer 273 is a semiconductor in whichthe concentration of each of an impurity imparting p-type conductivityand an impurity imparting n-type conductivity is 1×10²⁰ cm⁻³ or less andwhich has photoconductivity 100 times or more as high as darkconductivity. The i-type semiconductor layer 273 also includes, in itscategory, a semiconductor that contains an impurity element belonging toGroup 13 or Group 15 of the periodic table. In other words, since ani-type semiconductor has weak n-type electric conductivity when animpurity element for controlling valence electrons is not addedintentionally, the i-type semiconductor layer 273 includes, in itscategory, a semiconductor to which an impurity element imparting p-typeconductivity is added intentionally or unintentionally at the time ofdeposition or after the deposition.

The light-blocking layer 257 is closer to the substrate 221 than is thelight-receiving element and overlaps with the light-receiving element.The light-blocking layer 257 between the light-receiving element and thesealing layer 213 can prevent the light-receiving element from beingirradiated with light emitted from the light-emitting element 230.

The conductive layer 281 and the conductive layer 283 are electricallyconnected to the light-receiving element. The conductive layer 281preferably transmits light incident on the light-receiving element. Theconductive layer 283 preferably blocks light incident on thelight-receiving element.

It is preferable to provide an optical touch sensor between thesubstrate 222 and the sealing layer 213 because the optical touch sensoris less likely to be affected by light emitted from the light-emittingelement 230 and can have improved S/N ratio.

Specific Example 3

FIG. 9B shows another example of the light extraction portion 224 in thedisplay panel of one embodiment of the present invention. The displaypanel shown in FIG. 9B is capable of touch operation.

The display panel in FIG. 9B includes the substrate 221, the bondinglayer 223, the insulating layer 225, a plurality of transistors, theinsulating layer 227, an insulating layer 229 a, an insulating layer 229b, a plurality of light-emitting elements, the insulating layer 211, theinsulating layer 217, the sealing layer 213, the coloring layer 259, thelight-blocking layer 257, a plurality of light-receiving elements, aconductive layer 280, the conductive layer 281, the insulating layer255, the bonding layer 258, and the substrate 222.

FIG. 9B shows an example in which a light-receiving element is providedbetween the insulating layer 225 and the sealing layer 213. Since thelight-receiving element is provided between the insulating layer 225 andthe sealing layer 213, a conductive layer to which the light-receivingelement is electrically connected and a photoelectric conversion layerincluded in the light-receiving element can be formed using the samematerials and the same steps as a conductive layer and a semiconductorlayer included in the transistor 240. Thus, the display panel capable oftouch operation can be manufactured without a significant increase inthe number of manufacturing steps.

Specific Example 4

FIG. 10A shows another example of a display panel of one embodiment ofthe present invention. The display panel shown in FIG. 10A is capable oftouch operation.

The display panel in FIG. 10A includes the substrate 221, the bondinglayer 223, the insulating layer 225, a plurality of transistors, aconductive layer 156, the conductive layer 157, the insulating layer227, the insulating layer 229, a plurality of light-emitting elements,the insulating layer 211, the insulating layer 217, the sealing layer213, the coloring layer 259, the light-blocking layer 257, theinsulating layer 255, a conductive layer 272, a conductive layer 274, aninsulating layer 276, an insulating layer 278, a conductive layer 294, aconductive layer 296, the bonding layer 258, and the substrate 222.

FIG. 10A shows an example in which a capacitive touch sensor is providedbetween the insulating layer 255 and the sealing layer 213. Thecapacitive touch sensor includes the conductive layer 272 and theconductive layer 274.

The conductive layer 156 and the conductive layer 157 are electricallyconnected to the FPC 228 via the connector 215. The conductive layer 294and the conductive layer 296 are electrically connected to theconductive layer 274 via conductive particles 292. Thus, the capacitivetouch sensor can be driven via the FPC 228.

Specific Example 5

FIG. 10B shows another example of a display panel of one embodiment ofthe present invention. The display panel shown in FIG. 10B is capable oftouch operation.

The display panel in FIG. 10B includes the substrate 221, the bondinglayer 223, the insulating layer 225, a plurality of transistors, theconductive layer 156, the conductive layer 157, the insulating layer227, the insulating layer 229, a plurality of light-emitting elements,the insulating layer 211, the insulating layer 217, the sealing layer213, the coloring layer 259, the light-blocking layer 257, theinsulating layer 255, a conductive layer 270, the conductive layer 272,the conductive layer 274, the insulating layer 276, the insulating layer278, the bonding layer 258, and the substrate 222.

FIG. 10B shows an example in which a capacitive touch sensor is providedbetween the insulating layer 255 and the sealing layer 213. Thecapacitive touch sensor includes the conductive layer 272 and theconductive layer 274.

The conductive layer 156 and the conductive layer 157 are electricallyconnected to an FPC 228 a via a connector 215 a. The conductive layer270 is electrically connected to an FPC 228 b via a connector 215 b.Thus, the light-emitting element 230 and the transistor 240 can bedriven via the FPC 228 a, and the capacitive touch sensor can be drivenvia the FPC 228 b.

Specific Example 6

FIG. 11A shows another example of the light extraction portion 224 inthe display panel of one embodiment of the present invention.

The display panel in FIG. 11A includes the substrate 222, the bondinglayer 258, the insulating layer 225, a plurality of transistors, theinsulating layer 227, a conductive layer 237, the insulating layer 229a, the insulating layer 229 b, a plurality of light-emitting elements,the insulating layer 211, the sealing layer 213, the coloring layer 259,and a substrate 239.

The light-emitting element 230 includes the lower electrode 231, the ELlayer 233, and the upper electrode 235. The lower electrode 231 iselectrically connected to the source electrode or the drain electrode ofthe transistor 240 via the conductive layer 237. An end portion of thelower electrode 231 is covered with the insulating layer 211. Thelight-emitting element 230 has a bottom emission structure. The lowerelectrode 231 has a light-transmitting property and transmits lightemitted from the EL layer 233.

The coloring layer 259 is provided to overlap with the light-emittingelement 230, and light emitted from the light-emitting element 230 isextracted from the substrate 222 side through the coloring layer 259.The space between the light-emitting element 230 and the substrate 239is filled with the sealing layer 213. The substrate 239 can be formedusing a material similar to that of the substrate 221.

Specific Example 7

FIG. 11B shows another example of a display panel of one embodiment ofthe present invention.

The display panel in FIG. 11B includes the substrate 222, the bondinglayer 258, the insulating layer 225, a conductive layer 310 a, aconductive layer 310 b, a plurality of light-emitting elements, theinsulating layer 211, a conductive layer 212, the sealing layer 213, andthe substrate 239.

The conductive layer 310 a and the conductive layer 310 b, which areexternal connection electrodes of the display panel, can each beelectrically connected to an FPC or the like.

The light-emitting element 230 includes the lower electrode 231, the ELlayer 233, and the upper electrode 235. An end portion of the lowerelectrode 231 is covered with the insulating layer 211. Thelight-emitting element 230 has a bottom emission structure. The lowerelectrode 231 has a light-transmitting property and transmits lightemitted from the EL layer 233. The conductive layer 212 is electricallyconnected to the lower electrode 231.

The substrate 222 may have, as a light extraction structure, ahemispherical lens, a micro lens array, a film provided with an unevensurface structure, a light diffusing film, or the like. For example, thesubstrate 222 with a light extraction structure can be formed byattaching the above lens or film to a resin substrate with an adhesiveor the like having substantially the same refractive index as thesubstrate or the lens or film.

The conductive layer 212 is preferably, though not necessarily, providedbecause voltage drop due to the resistance of the lower electrode 231can be prevented. In addition, for a similar purpose, a conductive layerelectrically connected to the upper electrode 235 may be provided overthe insulating layer 211, the EL layer 233, the upper electrode 235, orthe like.

The conductive layer 212 can be a single layer or a stacked layer formedusing a material selected from copper, titanium, tantalum, tungsten,molybdenum, chromium, neodymium, scandium, nickel, or aluminum, an alloymaterial containing any of these materials as its main component, or thelike. The thickness of the conductive layer 212 can be, for example,greater than or equal to 0.1 μm and less than or equal to 3 μm,preferably greater than or equal to 0.1 μm and less than or equal to 0.5μm.

When a paste (e.g., silver paste) is used as a material for theconductive layer electrically connected to the upper electrode 235,metal particles forming the conductive layer aggregate; therefore, thesurface of the conductive layer is rough and has many gaps. Thus, evenwhen the conductive layer is formed over the insulating layer 211, forexample, it is difficult for the EL layer 233 to completely cover theconductive layer; accordingly, the upper electrode and the conductivelayer are electrically connected to each other easily, which ispreferable.

<Examples of Materials>

Next, materials and the like that can be used for a display panel of oneembodiment of the present invention are described. Refer also to theabove description in this specification.

Examples of materials used for the substrate 221, the substrate 222, andthe substrate 239 include glass, a metal, and an organic resin. Amaterial that transmits visible light is used for the substrate on thedisplay surface side of the display panel.

An organic resin, which has a specific gravity smaller than that ofglass, is preferably used for the substrate, in which case the displaypanel can be lightweight as compared with the case where glass is used.

Examples of a material having flexibility and a light-transmittingproperty with respect to visible light include glass that is thin enoughto have flexibility, polyester resins such as polyethylene terephthalate(PET) and polyethylene naphthalate (PEN), a polyacrylonitrile resin, apolyimide resin, a polymethyl methacrylate resin, a polycarbonate (PC)resin, a polyethersulfone (PES) resin, a polyamide resin, a cycloolefinresin, a polystyrene resin, a polyamide imide resin, and a polyvinylchloride resin. In particular, a material whose thermal expansioncoefficient is low is preferred, and for example, a polyamide imideresin, a polyimide resin, or PET can be suitably used. A substrate inwhich a glass fiber is impregnated with an organic resin or a substratewhose thermal expansion coefficient is reduced by mixing an organicresin with an inorganic filler can also be used.

The substrate may have a stacked structure of a layer of any of theabove-mentioned materials and a hard coat layer (e.g., a silicon nitridelayer) which protects a surface of the display panel from damage or thelike, a layer (e.g., an aramid resin layer) which can disperse pressure,or the like. Furthermore, to suppress a decrease in the lifetime of thelight-emitting element due to moisture and the like, an insulating filmwith low water permeability may be included in the stacked structure.

A material that transmits visible light is used for one of the bondinglayer 223 and the bonding layer 258 that is on the display surface sideof the display panel.

For the bonding layer, a resin that is curable at room temperature(e.g., a two-component-mixture-type resin), a light curable resin, athermosetting resin, or the like can be used. Examples of such resinsinclude an epoxy resin, an acrylic resin, a silicone resin, and a phenolresin. In particular, a material with low moisture permeability, such asan epoxy resin, is preferred.

Further, the resin may include a drying agent. For example, a substancethat adsorbs moisture by chemical adsorption, such as oxide of analkaline earth metal (e.g., calcium oxide or barium oxide), can be used.Alternatively, a substance that adsorbs moisture by physical adsorption,such as zeolite or silica gel, may be used. The drying agent ispreferably included because it can prevent an impurity such as moisturefrom entering the light-emitting element, thereby improving thereliability of the display panel.

In addition, it is preferable to mix a filler with a high refractiveindex (e.g., titanium oxide) into the resin, in which case theefficiency of light extraction from the light-emitting element can beimproved.

The bonding layer may also include a scattering member for scatteringlight. For example, the bonding layer can be a mixture of the aboveresin and particles having a refractive index different from that of theresin. The particles function as the scattering member for scatteringlight.

The difference in refractive index between the resin and the particleswith a refractive index different from that of the resin is preferably0.1 or more, further preferably 0.3 or more. Specifically, an epoxyresin, an acrylic resin, an imide resin, silicone, or the like can beused as the resin, and titanium oxide, barium oxide, zeolite, or thelike can be used as the particles.

Particles of titanium oxide or barium oxide are preferable because theyscatter light excellently. When zeolite is used, it can adsorb watercontained in the resin and the like, thereby improving the reliabilityof the light-emitting element.

The structure of the transistors in the display panel is notparticularly limited. For example, a forward staggered transistor or aninverted staggered transistor may be used. A top-gate transistor or abottom-gate transistor may be used. A semiconductor material used forthe transistors is not particularly limited, and for example, silicon orgermanium can be used. Alternatively, an oxide semiconductor containingat least one of indium, gallium, and zinc, such as an In—Ga—Zn-basedmetal oxide, may be used.

There is no particular limitation on the crystallinity of asemiconductor material used for the transistors, and an amorphoussemiconductor or a semiconductor having crystallinity (amicrocrystalline semiconductor, a polycrystalline semiconductor, asingle-crystal semiconductor, or a semiconductor partly includingcrystal regions) may be used. It is preferable that a semiconductorhaving crystallinity be used, in which case deterioration of thetransistor characteristics can be suppressed.

The light-emitting element included in the display panel includes a pairof electrodes (the lower electrode 231 and the upper electrode 235); andthe EL layer 233 between the pair of electrodes. One of the pair ofelectrodes functions as an anode and the other functions as a cathode.

The light-emitting element may have any of a top emission structure, abottom emission structure, and a dual emission structure. A conductivefilm that transmits visible light is used as the electrode through whichlight is extracted. A conductive film that reflects visible light ispreferably used as the electrode through which light is not extracted.

The conductive film that transmits visible light can be formed using,for example, indium oxide, indium tin oxide (ITO), indium zinc oxide,zinc oxide, or zinc oxide to which gallium is added. Alternatively, afilm of a metal material such as gold, silver, platinum, magnesium,nickel, tungsten, chromium, molybdenum, iron, cobalt, copper, palladium,or titanium; an alloy containing any of these metal materials; or anitride of any of these metal materials (e.g., titanium nitride) can beformed thin so as to have a light-transmitting property. Alternatively,a stack of any of the above materials can be used as the conductivefilm. For example, a stacked film of ITO and an alloy of silver andmagnesium is preferably used, in which case conductivity can beincreased. Further alternatively, graphene or the like may be used.

For the conductive film that reflects visible light, for example, ametal material such as aluminum, gold, platinum, silver, nickel,tungsten, chromium, molybdenum, iron, cobalt, copper, or palladium or analloy containing any of these metal materials can be used. Further,lanthanum, neodymium, germanium, or the like may be added to the metalmaterial or the alloy. Furthermore, an alloy containing aluminum (analuminum alloy) such as an alloy of aluminum and titanium, an alloy ofaluminum and nickel, or an alloy of aluminum and neodymium; or an alloycontaining silver such as an alloy of silver and copper, an alloy ofsilver, copper, and palladium, or an alloy of silver and magnesium canbe used for the conductive film. An alloy of silver and copper ispreferable because of its high heat resistance. Further, when a metalfilm or a metal oxide film is stacked on and in contact with an aluminumalloy film, oxidation of the aluminum alloy film can be prevented.Examples of a material for the metal film or the metal oxide film aretitanium and titanium oxide. Alternatively, the above conductive filmthat transmits visible light and a film containing a metal material maybe stacked. For example, a stacked film of silver and ITO or a stackedfilm of an alloy of silver and magnesium and ITO can be used.

Each of the electrodes can be formed by an evaporation method or asputtering method. Alternatively, a discharging method such as an inkjetmethod, a printing method such as a screen printing method, or a platingmethod may be used.

When a voltage higher than the threshold voltage of the light-emittingelement is applied between the lower electrode 231 and the upperelectrode 235, holes are injected to the EL layer 233 from the anodeside and electrons are injected to the EL layer 233 from the cathodeside. The injected electrons and holes are recombined in the EL layer233 and a light-emitting substance contained in the EL layer 233 emitslight.

The EL layer 233 includes at least a light-emitting layer. In additionto the light-emitting layer, the EL layer 233 may further include one ormore layers containing any of a substance with a high hole-injectionproperty, a substance with a high hole-transport property, ahole-blocking material, a substance with a high electron-transportproperty, a substance with a high electron-injection property, asubstance with a bipolar property (a substance with a high electron- andhole-transport property), and the like.

For the EL layer 233, either a low molecular compound or a highmolecular compound can be used, and an inorganic compound may also beused. Each of the layers included in the EL layer 233 can be formed byany of the following methods: an evaporation method (including a vacuumevaporation method), a transfer method, a printing method, an inkjetmethod, a coating method, and the like.

The insulating layer 225 and the insulating layer 255 can each be formedusing an inorganic insulating material. It is particularly preferable touse an insulating film with low water permeability, in which case ahighly reliable display panel can be provided.

The insulating layer 227 has an effect of preventing diffusion ofimpurities into a semiconductor included in the transistor. As theinsulating layer 227, an inorganic insulating film such as a siliconoxide film, a silicon oxynitride film, a silicon nitride film, a siliconnitride oxide film, or an aluminum oxide film can be used.

As each of the insulating layers 229, 229 a, and 229 b, an insulatingfilm with a planarization function is preferably selected in order toreduce surface unevenness due to the transistor or the like. Forexample, an organic material such as a polyimide resin, an acrylicresin, or a benzocyclobutene-based resin can be used. Other than suchorganic materials, it is also possible to use a low-dielectric constantmaterial (a low-k material) or the like. Note that the planarizationinsulating film may have a stacked structure of any of insulating filmsformed of these materials and inorganic insulating films.

The insulating layer 211 is provided to cover an end portion of thelower electrode 231. In order that the insulating layer 211 be favorablycovered with the EL layer 233 and the upper electrode 235 formedthereover, a side wall of the insulating layer 211 preferably has atilted surface with continuous curvature.

As a material for the insulating layer 211, a resin or an inorganicinsulating material can be used. As the resin, for example, a polyimideresin, a polyamide resin, an acrylic resin, a siloxane resin, an epoxyresin, or a phenol resin can be used. In particular, either a negativephotosensitive resin or a positive photosensitive resin is preferablyused for easy formation of the insulating layer 211.

There is no particular limitation to the method for forming theinsulating layer 211; a photolithography method, a sputtering method, anevaporation method, a droplet discharging method (e.g., an inkjetmethod), a printing method (e.g., a screen printing method or an off-setprinting method), or the like may be used.

The insulating layer 217 can be formed using an inorganic insulatingmaterial, an organic insulating material, or the like. As the organicinsulating material, for example, a negative or positive photosensitiveresin, a non-photosensitive resin, or the like can be used. Instead ofthe insulating layer 217, a conductive layer may be formed. For example,the conductive layer can be formed using a metal material such astitanium or aluminum. When a conductive layer is used instead of theinsulating layer 217 and the conductive layer is electrically connectedto the upper electrode 235, voltage drop due to the resistance of theupper electrode 235 can be prevented. The insulating layer 217 may haveeither a tapered shape or an inverse tapered shape.

Each of the insulating layers 276, 278, 291, 293, and 295 can be formedusing an inorganic insulating material or an organic insulatingmaterial. It is particularly preferable to use an insulating film with aplanarization function for each of the insulating layers 278 and 295 inorder to reduce surface unevenness due to a sensor element.

For the sealing layer 213, a resin that is curable at room temperature(e.g., a two-component-mixture-type resin), a light curable resin, athermosetting resin, or the like can be used. For example, a polyvinylchloride (PVC) resin, an acrylic resin, a polyimide resin, an epoxyresin, a silicone resin, a polyvinyl butyral (PVB) resin, an ethylenevinyl acetate (EVA) resin, or the like can be used. A drying agent maybe contained in the sealing layer 213. In the case where light emittedfrom the light-emitting element 230 is extracted outside through thesealing layer 213, the sealing layer 213 preferably includes a fillerwith a high refractive index or a scattering member. Materials for thedrying agent, the filler with a high refractive index, and thescattering member are similar to those that can be used for the bondinglayer 258.

Each of the conductive layers 156, 157, 294, and 296 can be formed usingthe same material and the same step as a conductive layer included inthe transistor or the light-emitting element. The conductive layer 280can be formed using the same material and the same step as a conductivelayer included in the transistor.

For example, each of the conductive layers can be formed to have asingle-layer structure or a stacked-layer structure using any of metalmaterials such as molybdenum, titanium, chromium, tantalum, tungsten,aluminum, copper, neodymium, and scandium, and an alloy materialcontaining any of these elements. Each of the conductive layers may beformed using a conductive metal oxide. As the conductive metal oxide,indium oxide (e.g., In₂O₃), tin oxide (e.g., SnO₂), zinc oxide (ZnO),ITO, indium zinc oxide (e.g., In₂O₃—ZnO), or any of these metal oxidematerials in which silicon oxide is contained can be used.

Each of the conductive layers 237, 212, 310 a, and 310 b can also beformed using any of the above metal materials, alloy materials, andconductive metal oxides.

Each of the conductive layers 272, 274, 281, and 283 is a conductivelayer with a light-transmitting property. The conductive layer can beformed using, for example, indium oxide, ITO, indium zinc oxide, zincoxide, zinc oxide to which gallium is added, or the like. The conductivelayer 270 can be formed using the same material and the same step as theconductive layer 272.

As the conductive particles 292, particles of an organic resin, silica,or the like coated with a metal material are used. It is preferable touse nickel or gold as the metal material because contact resistance canbe reduced. It is also preferable to use particles each coated withlayers of two or more kinds of metal materials, such as particles coatedwith nickel and further with gold.

For the connector 215, it is possible to use a paste-like or sheet-likematerial which is obtained by mixture of metal particles and athermosetting resin and for which anisotropic electric conductivity isprovided by thermocompression bonding. As the metal particles, particlesin which two or more kinds of metals are layered, for example, nickelparticles coated with gold are preferably used.

The coloring layer 259 is a colored layer that transmits light in aspecific wavelength range. For example, a red (R) color filter fortransmitting light in a red wavelength range, a green (G) color filterfor transmitting light in a green wavelength range, a blue (B) colorfilter for transmitting light in a blue wavelength range, or the likecan be used. Each coloring layer is formed in a desired position withany of various materials by a printing method, an inkjet method, anetching method using a photolithography method, or the like.

The light-blocking layer 257 is provided between the adjacent coloringlayers 259. The light-blocking layer 257 blocks light emitted from theadjacent light-emitting element, thereby preventing color mixturebetween adjacent pixels. Here, the coloring layer 259 is provided suchthat its end portion overlaps with the light-blocking layer 257, wherebylight leakage can be reduced. The light-blocking layer 257 can be formedusing a material that blocks light emitted from the light-emittingelement, for example, a metal material, a resin material including apigment or a dye, or the like. Note that the light-blocking layer 257 ispreferably provided in a region other than the light extraction portion224, such as the driver circuit portion 226, as illustrated in FIG. 8B,in which case undesired leakage of guided light or the like can beprevented.

The insulating layer 261 covering the coloring layer 259 and thelight-blocking layer 257 is preferably provided because it can preventan impurity such as a pigment included in the coloring layer 259 or thelight-blocking layer 257 from diffusing into the light-emitting elementor the like. For the insulating layer 261, a light-transmitting materialis used, and an inorganic insulating material or an organic insulatingmaterial can be used. An insulating film with low water permeability maybe used for the insulating layer 261. Note that the insulating layer 261is not necessarily provided.

<Example of Manufacturing Method>

Next, an example of a method for manufacturing a display panel of oneembodiment of the present invention will be described with reference toFIGS. 12A to 12C and FIGS. 13A to 13C. Here, the manufacturing method isdescribed using the display panel of Specific Example 1 (FIG. 8B) as anexample.

First, a separation layer 313 is formed over a formation substrate 311,and the insulating layer 225 is formed over the separation layer 313.Next, the plurality of transistors, the conductive layer 157, theinsulating layer 227, the insulating layer 229, the plurality oflight-emitting elements, and the insulating layer 211 are formed overthe insulating layer 225. An opening is formed in the insulating layers211, 229, and 227 to expose the conductive layer 157 (FIG. 12A).

In addition, a separation layer 307 is formed over a formation substrate305, and the insulating layer 255 is formed over the separation layer307. Next, the light-blocking layer 257, the coloring layer 259, and theinsulating layer 261 are formed over the insulating layer 255 (FIG.12B).

The formation substrate 311 and the formation substrate 305 can each bea glass substrate, a quartz substrate, a sapphire substrate, a ceramicsubstrate, a metal substrate, an organic resin substrate, or the like.

For the glass substrate, for example, a glass material such asaluminosilicate glass, aluminoborosilicate glass, or barium borosilicateglass can be used. When the temperature of heat treatment performedlater is high, a substrate having a strain point of 730° C. or higher ispreferably used. Note that when containing a large amount of bariumoxide, the glass substrate can be heat-resistant and more practical.Alternatively, crystallized glass or the like may be used.

In the case where a glass substrate is used as the formation substrate,an insulating film such as a silicon oxide film, a silicon oxynitridefilm, a silicon nitride film, or a silicon nitride oxide film ispreferably formed between the formation substrate and the separationlayer, in which case contamination from the glass substrate can beprevented.

The separation layer 313 and the separation layer 307 each have asingle-layer structure or a stacked-layer structure containing anelement selected from tungsten, molybdenum, titanium, tantalum, niobium,nickel, cobalt, zirconium, zinc, ruthenium, rhodium, palladium, osmium,iridium, and silicon; an alloy material containing any of the elements;or a compound material containing any of the elements. A crystalstructure of a layer containing silicon may be amorphous, microcrystal,or polycrystal.

The separation layer can be formed by a sputtering method, a plasma CVDmethod, a coating method, a printing method, or the like. Note that acoating method includes a spin coating method, a droplet dischargemethod, and a dispensing method.

In the case where the separation layer has a single-layer structure, atungsten layer, a molybdenum layer, or a layer containing a mixture oftungsten and molybdenum is preferably formed. Alternatively, a layercontaining an oxide or an oxynitride of tungsten, a layer containing anoxide or an oxynitride of molybdenum, or a layer containing an oxide oran oxynitride of a mixture of tungsten and molybdenum may be formed.Note that the mixture of tungsten and molybdenum corresponds to an alloyof tungsten and molybdenum, for example.

In the case where the separation layer is formed to have a stacked-layerstructure including a layer containing tungsten and a layer containingan oxide of tungsten, the layer containing an oxide of tungsten may beformed as follows: the layer containing tungsten is formed first and aninsulating film formed of an oxide is formed thereover, so that thelayer containing an oxide of tungsten is formed at the interface betweenthe tungsten layer and the insulating film. Alternatively, the layercontaining an oxide of tungsten may be formed by performing thermaloxidation treatment, oxygen plasma treatment, nitrous oxide (N₂O) plasmatreatment, treatment with a highly oxidizing solution such as ozonewater, or the like on the surface of the layer containing tungsten.Plasma treatment or heat treatment may be performed in an atmosphere ofoxygen, nitrogen, or nitrous oxide alone, or a mixed gas of any of thesegasses and another gas. Surface condition of the separation layer ischanged by the plasma treatment or heat treatment, whereby adhesionbetween the separation layer and the insulating layer formed later canbe controlled.

Each of the insulating layers can be formed by a sputtering method, aplasma CVD method, a coating method, a printing method, or the like. Forexample, the insulating layer is formed at a temperature of higher thanor equal to 250° C. and lower than or equal to 400° C. by a plasma CVDmethod, whereby the insulating layer can be a dense film with very lowwater permeability.

Then, a material for the sealing layer 213 is applied to a surface ofthe formation substrate 305 over which with the coloring layer 259 andthe like are formed or a surface of the formation substrate 311 overwhich the light-emitting element 230 and the like are formed, and theformation substrate 311 and the formation substrate 305 are attached sothat these two surfaces face each other with the sealing layer 213positioned therebetween (FIG. 12C).

Next, the formation substrate 311 is separated, and the exposedinsulating layer 225 and the substrate 221 are attached to each otherwith the bonding layer 223. Further, the formation substrate 305 isseparated, and the exposed insulating layer 255 and the substrate 222are attached to each other with the bonding layer 258. Although thesubstrate 222 does not overlap with the conductive layer 157 in FIG.13A, the substrate 222 may overlap with the conductive layer 157.

Any of a variety of methods can be used as appropriate for theseparation process. For example, when a layer including a metal oxidefilm is formed as the separation layer on the side in contact with thelayer to be separated, the metal oxide film is embrittled bycrystallization, whereby the layer to be separated can be separated fromthe formation substrate. Alternatively, when an amorphous silicon filmcontaining hydrogen is formed as the separation layer between theformation substrate having high heat resistance and the layer to beseparated, the amorphous silicon film is removed by laser lightirradiation or etching, whereby the layer to be separated can beseparated from the formation substrate. Alternatively, after a layerincluding a metal oxide film is formed as the separation layer on theside in contact with the layer to be separated, the metal oxide film isembrittled by crystallization, and part of the separation layer isremoved by etching using a solution or a fluoride gas such as NF₃, BrF₃,or ClF₃, whereby the separation can be performed at the embrittled metaloxide film. Furthermore, a method may be used in which a film containingnitrogen, oxygen, hydrogen, or the like (for example, an amorphoussilicon film containing hydrogen, an alloy film containing hydrogen, analloy film containing oxygen, or the like) is used as the separationlayer, and the separation layer is irradiated with laser light torelease the nitrogen, oxygen, or hydrogen contained in the separationlayer as a gas, thereby promoting separation between the layer to beseparated and the formation substrate. Alternatively, it is possible touse a method in which the formation substrate provided with the layer tobe separated is removed mechanically or by etching using a solution or afluoride gas such as NF₃, BrF₃, or ClF₃, or the like. In this case, theseparation layer is not necessarily provided.

Further, the separation process can be conducted easily by combinationof the above-described separation methods. In other words, separationcan be performed with physical force (by a machine or the like) afterperforming laser light irradiation, etching on the separation layer witha gas, a solution, or the like, or mechanical removal with a sharpknife, scalpel or the like so that the separation layer and the layer tobe separated can be easily separated from each other.

Separation of the layer to be separated from the formation substrate maybe carried out by filling the interface between the separation layer andthe layer to be separated with a liquid. Further, the separation may beconducted while pouring a liquid such as water.

As another separation method, in the case where the separation layer isformed using tungsten, it is preferable that the separation be performedwhile etching the separation layer using a mixed solution of ammoniumwater and a hydrogen peroxide solution.

Note that the separation layer is not necessary in the case whereseparation at the interface between the formation substrate and thelayer to be separated is possible. For example, glass is used as theformation substrate, an organic resin such as polyimide, polyester,polyolefin, polyamide, polycarbonate, or acrylic is formed in contactwith the glass, and an insulating film, a transistor, and the like areformed over the organic resin. In this case, heating the organic resinenables the separation at the interface between the formation substrateand the organic resin. Alternatively, separation at the interfacebetween a metal layer and the organic resin may be performed in thefollowing manner: the metal layer is provided between the formationsubstrate and the organic resin and current is made to flow in the metallayer so that the metal layer is heated.

Lastly, an opening is formed in the insulating layer 255 and the sealinglayer 213 to expose the conductive layer 157 (FIG. 13B). In the casewhere the substrate 222 overlaps with the conductive layer 157, theopening is formed also in the substrate 222 and the bonding layer 258 sothat the conductive layer 157 is exposed (FIG. 13C). The method forforming the opening is not particularly limited and may be, for example,a laser ablation method, an etching method, an ion beam sputteringmethod, or the like. As another method, a cut may be made in a film overthe conductive layer 157 with a sharp knife or the like and part of thefilm may be separated by physical force.

In the above-described manner, the display panel of one embodiment ofthe present invention can be manufactured.

As described above, a display panel of one embodiment of the presentinvention includes two substrates; one is the substrate 222 and theother is the substrate 221 or the substrate 239. The light-emittingdevice can be formed with two substrates even when including a touchsensor. Owing to the use of the minimum number of substrates,improvement in light extraction efficiency and improvement in clarity ofdisplay can be easily achieved.

This embodiment can be combined with any other embodiment asappropriate.

EXPLANATION OF REFERENCE

101: display unit, 101 a: display unit, 101 b: display unit, 101 c:display unit, 101 d: display unit, 103: housing, 103 a: housing, 103 b:housing, 106: joint portion, 110: display device, 120: display device,130: display device, 140: display device, 156: conductive layer, 157:conductive layer, 201: support, 203: display panel, 203 a: displayregion, 203 b: non-display region, 205: projection, 207: projection,211: insulating layer, 212: conductive layer, 213: sealing layer, 215:connector, 215 a: connector, 215 b: connector, 217: insulating layer,221: substrate, 222: substrate, 223: bonding layer, 224: lightextraction portion, 225: insulating layer, 226: driver circuit portion,227: insulating layer, 228: FPC, 228 a: FPC, 228 b: FPC, 229: insulatinglayer, 229 a: insulating layer, 229 b: insulating layer, 230:light-emitting element, 231: lower electrode, 233: EL layer, 235: upperelectrode, 237: conductive layer, 239: substrate, 240: transistor, 255:insulating layer, 257: light-blocking layer, 258: bonding layer, 259:coloring layer, 261: insulating layer, 270: conductive layer, 271:p-type semiconductor layer, 272: conductive layer, 273: i-typesemiconductor layer, 274: conductive layer, 275: n-type semiconductorlayer, 276: insulating layer, 278: insulating layer, 280: conductivelayer, 281: conductive layer, 283: conductive layer, 291: insulatinglayer, 292: conductive particle, 293: insulating layer, 294: conductivelayer, 295: insulating layer, 296: conductive layer, 301: region, 303:region, 305: formation substrate, 307: separation layer, 310 a:conductive layer, 310 b: conductive layer, 311: formation substrate,313: separation layer.

This application is based on Japanese Patent Application serial no.2013-090873 filed with Japan Patent Office on Apr. 24, 2013, the entirecontents of which are hereby incorporated by reference.

1. A display device comprising: a first display unit and a seconddisplay unit, each of which comprises: a display panel including adisplay region and a non-display region; and a support having a firstsurface overlapped with the display region and a second surfaceoverlapped with part of the display region and the non-display region;and a foldable housing comprising a joint portion, wherein the firstdisplay unit and the second display unit are placed in the foldablehousing with the joint portion therebetween.
 2. The display deviceaccording to claim 1, wherein the display panel is a flexible displaypanel.
 3. The display device according to claim 1, wherein the displaypanel further comprises a touch sensor.
 4. The display device accordingto claim 1, wherein in an opened state of the display device, the secondsurface in the first display unit and the second surface in the seconddisplay unit face each other.
 5. The display device according to claim1, wherein the first display unit and the second display unit aredetachable from the foldable housing.
 6. The display device according toclaim 1, wherein a distance between the first display unit and thesecond display unit is adjustable.
 7. The display device according toclaim 1, wherein the support has a third surface which is opposite tothe second surface, and wherein the third surface is overlapped withpart of the display region and the non-display region.
 8. The displaydevice according to claim 1, wherein the display panel is alight-emitting device.
 9. A display device comprising: a first displayunit and a second display unit, each of which comprises: a display panelincluding a display region and a non-display region; and a supporthaving a first surface overlapped with the display region and a secondsurface overlapped with part of the display region and the non-displayregion; and a foldable housing, wherein the first display unit and thesecond display unit are placed in the foldable housing, and wherein inan opened state of the display device, the first display unit and thesecond display unit are in contact with each other so as to display asingle image across two display units without a bezel therebetween. 10.The display device according to claim 9, wherein the display panel is aflexible display panel.
 11. The display device according to claim 9,wherein the display panel further comprises a touch sensor.
 12. Thedisplay device according to claim 9, wherein in the opened state of thedisplay device, the second surface in the first display unit and thesecond surface in the second display unit face each other.
 13. Thedisplay device according to claim 9, wherein the first display unit andthe second display unit are detachable from the foldable housing. 14.The display device according to claim 9, wherein the support has a thirdsurface which is opposite to the second surface, and wherein the thirdsurface is overlapped with part of the display region and thenon-display region.
 15. The display device according to claim 9, whereinthe display panel is a light-emitting device.
 16. A display devicecomprising: a support comprising a first surface, a second surface, athird surface and a fourth surface; and a display panel comprising anorganic electroluminescent material on the first surface of the support,wherein two side edges of the display panel are curved, wherein the twoside edges reach the fourth surface of the support opposite to the firstsurface, and wherein an image is displayed on the first surface, part ofthe second surface, and part of the third surface.
 17. The displaydevice according to claim 16, wherein the display panel is a flexibledisplay panel.
 18. The display device according to claim 16, wherein thedisplay panel further comprises a touch sensor.
 19. The display deviceaccording to claim 16, wherein the support comprises a plastic or arubber.